Hydraulic ram apparatus



May 8, 1962 H. NORTON ETAL 3,033,170

HYDRAULIC RAM APPARATUS Filed Sept. 25, 1959 l 2 Sheets-SheenI 1 /7 4 a1 2f 1g Ild L [Qn 24 /3 22 23 /a/P FIG. F/G. 2.

lNv ENTORS HENQY Noz-roN HERBERT V. NorroN L EsLxE B. Narren DouLAs ENORTON ATTQQNEYS May 8, 1962 Filed Sept. 2 5, 1959 HA NORTON ETALHYDRAULIC RAM APPARATUS 2 Sheets-Sheet 2 lNvENToRS HENRY NoZTON HERBERTV. NotzvoN LESLIE B. NoR'roN bouc-.As E.Nosz1'o- ATTORNEY:

United States Patent O M 3,033,170 HYDRAULIC RAM APPARATUS Henry Norton,Hubert Veare Norton, Leslie Buckingham Norton, and Douglas Edwin Norton,all of Horley, England, assignors to Norton Tool Company Limited,Horley, England, a company of Great Britain Filed Sept. 25, 1959, Ser.No. 842,509 Claims priority, application Great Britain Oct. 1, 1958 6Claims. (Cl. 121-38) This invention relates to hydraulic ram apparatussuitable for numerous applications, for instance, for actuating machinetools such as hydraulic presses, Shapers and slotters, power steeringgear, power transmission systems, mechanical handling equipment and rockdrills.

It is an object of the invention to provide a hydraulic ram apparatuswhich is easily controllable to provide a variety of motions withoutexcessive energy losses. Although in its basic form the apparatus isunusually simple it is capable of elaboration to provide a wider varietyof motions.

Hydraulic ram apparatus according to the present invention comprises, inits simplest form, a double acting ram having differential effectiveareas, a connecting passage between the two ram chambers containingautomatic unloader valve means having an open condition maintained at.above a predetermined pressure in the ram chamber of smaller effectivearea to permit flow from this ram chamber to the ram chamber of largereffective area and adapted to be brought into said open condition onlyon .attainment of a pressure substantially in excess of saidpredetermined pressure a source of hydraulic fluid under pressure (eg. apump) in permanent communication with the ram chamber of smallereffective area, and a control valve communicating with the ram chamberof larger effective `area and operable to control release of hydraulicfluid.

This simple form of the apparatus provides for working and returnstrokes of controllable length and duration utilising a single controlvalve, as will be described in more detail hereinafter.

The automatic unloader valve may comprise a cylinder containing aspring-loaded piston of relatively large area controlling an outlet portin the cylinder Wall and carrying an inlet closure member which can seaton a seating of smaller .area than the piston and which is exposed tothe Valve' inlet, the piston being exposed to the inlet only when theclosure member is lifted from its seating, for instance by theapplication to the closure member of the said predetermined highpressure.

The automatic unloader valve may be provided with relief means betweenthe piston and the seating operative to facilitate re-seating of theinlet closure member by relieving hydraulic fluid which might otherwisebe trapped between the piston and the seating.

A preferred form of the invention provides a fast approach during theworking stroke. In this form of the invention there is a source ofhydraulic fluid at low pressure communicating with the ram chamber oflarger effective area through a non-return valve. In such apparatusthere may be an unloader valve between the supply of hydraulic fluid atlow pressure and the last mentioned non-return valve, to unload the saidsupply when this non-return valve is closed.

The control valve is preferably such that the pressure at which it opensto permit fluid to escape from the apparatus is a function of themagnitude of a force applied to an acuating member of the valve. Such avalve enables the working force exerted by the ram on its working stroketo be controlled, since when the Working force is being applied by theram the control valve 3,033,170 Patented May 8, 1962 will allowsufficient iluid to escape to maintain the effective fluid pressure onthe ram at the desired value.

ln a further form of the invention providing a further range of motions,the simple types of control valve described above are replaced by a moreelaborate control unit as described in the present applicants U.S.Patent No. 2,980,064 issued April 18, 1961.

The invention may be performed in various ways, and some specicembodiments will now be described by way of example with reference tothe accompanying diagrammatic drawings, in which:

FIGURE 1 shows a simple form of hydraulic ram apparatus embodying theinvention, as applied to a hydraulic press, with the ram stationary inits fully raised position;

FIGURE 2 shows the apparatus of FIGURE l during the approach portion ofthe Working stroke;

FIGURE 3 shows the apparatus of FIGURE l during the return stroke;

FIGURE 4 shows a more elaborate form of apparatus, during a fastapproach portion of the working stroke; and

FIGURE 5 shows the apparatus of FIGURE 4 during the working portion ofthe working stroke.

In `all the drawings, identical parts have been given the same referencenumerals. It is to be understood that the drawings are highlydiagrammatic, with the object of illustrating the principles of theinvention and the way the various valves and the like operate ratherthan the details of design .and construction.

rl`he hydraulic ram apparatus shown in FIGURES 1 to 3 comprises a doubleacting ram 10 having a cylinder 11 and a piston 12. The piston 12 has apiston rod 13 provided with a working head 14 which is required to presswith a large force upon a work piece 15 resting on a base 16. The pistondivides the cylinder into an upper chamber 17 and a lower chamber 18.Hydraulic fluid for operating the ram is drawn from a reservoir 19 by `ahigh pressure pump 20. The pump delivers fluid through a line 21 into aconnecting line or passage 22, 23,- 24, 25 which connects the chambers17 .and 18 and which contains an automatic unloader valve 26. Theunloader valve 26 comprises a cylinder 27 containing a piston 28 urgeddownwardly by a spring 29. The piston is provided with an inlet closuremember 30 which can seat on an inlet seating 31, and itself controls theoutlet port 32 in the wall of the cylinder 27. Communicating with thesaid connecting line between the sections 24 and 25 thereof is a line 33which leads to a control valve 34. The control valve 34 has a piston 35provided with a closure member 36 which can seat on a seating 37, the

piston can be loaded by a spring 3S the force of which.

can `be adjusted by a manual control lever 39. A return line 40 leadsfrom the control valve 34 to the reservoir 19.

The apparatus works as follows. shown in FIGURE 1 the piston 12 hasfinished a return stroke and is up against a dead stop 41 at the top ofthe cylinder 11, and the control valve 34 is in a position in which itpermits free flow from the line 33 to the return line 40. The iiow fromthe pump 20 through the connecting line sections 23 and 24 into the line33 is sufficient to hold the unloader valve 26 open, as will bedescribed later. In this condition the iiuid flow is as indicated by thearrows. When ya working stroke is to be performed the control lever 39is moved towards the left as Shown in FlGURE 2 to increase the loadingof the spring 38 and close the valve 34. The pressure then risessuiciently to overcome the resistance of the piston 12 so that thelatter moves downwardly on the approach portion of the working stroke.As the piston 12 descends, uid is discharged from the lower chamber 18and passes freely through the connecting line sections In the condition-22, 23, the open unloader valve 26, and the connecting line sections 24,2S into the upper chamber 17, as shown by the arrows in FIGURE 2, sothat the pump 20 has only to supply enough fluid to malte up thedifference in the volumes of these chambers. The operator can slow downthe speed of approach by adjusting the control lever 39 towards theright. At the end of the approach, i.e. when the head 14 meets theworkpiece 15, the pressure will build up as required until the valve 34-re-opens. This re-opening may take place voluntarily by the operatormoving the control lever 39 towards the right, or automatically when thepressure overcomes the loading of the spring 38 with the control leverin its lefthaud position. In the latter case the maximum working forcewill continue to be applied to the work-piece so long as the controllever remains in the left-hand position. Movement of the control levertowards the right progressively eases the working force, that is to say,the position f the lever determines the magnitude of the working force.turn stroke as shown in FIGURE 3, the control lever 39 is moved fully tothe right, to open the valve 34. The piston 12 can now rise freely, thefluid in the upper chamber 17 being discharged freely through the lines25 and 33, and through the valve 34, and all the delivery of the pump 20passing into the lower chamber 18 so that there is no flow through theunloader valve 26 which accordingly closes. Since the pump 2G is at alltimes in communication with the lower chamber 18 the return movement ofthe piston begins practically instan taneously on opening the valve 34.When the piston 12 comes up against the dead stop 41 and can rise nofurther, the pressure in the lines 21, 22 and 23 will rise to a highvalue, exerting suficient force on the closure member 3G of the unloadervalve to lift it from its seating. As soon as this valve lifts, thepressure is applied to the whole under the surface of the piston 28, sothat the piston is raised sufliciently to expose the port 32. Theapparatus is now back in the condition shown in FIGURE l, so that thecycle described can be repeated.

It is not necessary for the return stroke to continue as far as the deadstop 41, since the return motion can be checked by moving the controllever 39 to the left to close the valve 34, whereupon another workingstroke begins.

This apparatus thus provides for working and return strokes ofcontrollable length and duration utilizing a single simple controlvalve.

The apparatus shown in FIGURES 4 and 5 is intended to provide a fastapproach, and includes some other refinements. Its basic parts areessentially the same as those of the apparatus of` FIGURES 1 to 3, withsome additions. In addition to the high pressure pump 20 there isprovided a low pressure pump 5) which is connected through a lowpressure unloader valve 51 and a non-return valve 52 to a line 53 whichleads to the upper ram chamber 17 via the line 25. The low pressureunloader valve S1 has a valve member Se which is urged towards a seating55 by a spring 56 and which is provided with a grooved stem 57 so thatwhen it is lifted from its seating in a manner to be described, lowpressure fluid can escape from the valve 51 through a return line 58.When the valve member 54 is closed, however, low pressure fluid mustpass to the non-return valve 52. In order to ensure that the non-returnvalve 52 is not prevented from seating promptly by trapped low pressurefluid when it returns to its closed condition, a piston 59 is providedwhich holds the valve member 54 slightly open whenever the pressure inthe line 53 is greater than the delivery pressure of the low pressurepump 50. One side of the piston 59 is exposed to the pressure on theoutlet side of the non-return valve through a passage 60, while itsother side is exposed to the delivery pressure of the pump S0 within thevalve 51.

The high pressure unloader valve 26 is `also equipped To cause thepiston 12 to rise on its rewith means for ensuring that trapped fluidcannot prevent it from seating promptly. In this case the lower part ofthe cylinder 27 communicates through a passage 61 with one end of acylinder 62 in which is a piston 63. The space behind this piston is incommunication with the upper part of the cylinder 17 through a passage64. When the unloader valve 26 is nearing its closed position and hasclosed the port 32, fluid beneath the piston 28 will not be trappedsince it will merely be expelled into the cylinder 62, the piston 63being moved to the left correspondingly, there being in effect adisplacement of fluid from the space of decreasing volume beneath thepiston 28 into the space of increasing volume above it.

This apparatus works as follows. When the control lever is moved to theleft as shown in FIGURE 4 to initiate the fast approach portion of theworking stroke, fluid enters the upper ram chamber 17 not only from thehigh pressure pump 20 and from the lower ram chamber 18 as shown inFIGURE 2, but also from the low pressure pump Sil through the lowpressure unloader valve 51, the non-return valve 52 and the line 53. Theunloader valve 51 is so constructed that at the relatively low pressureneeded to move the piston 12 in the approach portion of its workingstroke the valve member 54 remains on its seating. In view of the largevolume of uid supplied to the upper ram chamber 17 from these threesources, the piston 12 will descend rapidly. When the piston 12 meetsresistance, i.e, when the head 14 touches the work-piece as shown inFIGURE 5, pressure will rapidly build up. The increase in pressure Willopen the low pressure unloader valve S1, permitting low pressure fluidto return to the reservoir through the return line 5S, so that thenon-return valve S2 and the bleed valve 60 closes. The low pressure partof the apparatus is now isolated from the high pressure part, whichcontinues to operate in the manner described in relation to FIGURES 1 to3.

What We claim as our invention and desire to secure by Letters Patentis:

1. Hydraulic double acting ram apparatus comprising a ram cylinderhaving a side wall and end Walls, a piston in said cylinder, a pistonrod extending from said piston through one of said end walls, saidcylinder, said piston and said piston rod defining a first ram chamberand a second ram chamber of smaller effective area than said iirst ramchamber, connecting passage means between said first and second ramchambers, automatic pressuresensitive unloader valve means disposed insaid eonnecting passage means and having an inlet side connected to saidsecond ram chamber, said valve means having an open condition maintainedat above a predetermined pressure in said second ram chamber and aclosed condition maintained at below said predetermined pressure, saidvalve means in said open condition permitting ow of hydraulic fluid inthe direction from said second ram chamber to said first ram chamber,and in said closed position preventing such flow, said valve means beingadapted to be brought into said open condition only on the attainment ofa high pressure subtsantially in excess of said predetermined pressureapplied to said inlet side, a source of hydraulic fluid under pressurein permanent communication with said second ram chamber, and a manualcontrol valve operable to control release of hydraulic fluid andcommunicating with said first ram chamber.

2. Hydraulic ram apparatus according to claim l, in which said automaticunloader valve comprises a cylinder having an outlet port, an inletconnection to said cylinder, a seating adjacent said inlet connection, apiston slidable in said cylinder and having a cross-section greater thanthe cross-section of said seating, an inlet closure member carried bysaid piston in alignment with said seating, a spring loading said pistontowards a position in which said inlet closure member seats on saidseating, said piston when said inlet closure member is seated on saidseating being isolated from said inlet connection, said piston when saidinlet closure member is clear of said seating being exposed to saidinlet connection through said seating, and said piston controlling saidoutlet port.

3. Hydraulic ram apparatus according to claim 2, in which said automaticunloader valve is provided with relief means, said relief means -beingconnected to said cylinder between said piston and said seating, saidrelief means being operative to facilitate re-seating of said inletclosure member.

4, Hydraulic ram apparatus according to claim l in which said controlvalve comprises a manual actuating member, a closure member, and meansconnecting said actuating member to said closure member to impart tosaid closure member a closing force which is a function of the manualforce applied to said actuating member.

5. Hydraulic double-acting ram apparatus comprising a ram cylinderhaving a side wall and end Walls, a piston in said cylinder, a pistonrod extending from said piston through one of said end Walls, saidcylinder, said piston and said piston rod dening a first ram chamber anda second ram chamber of smaller elective area than said first ramchamber, connecting passage means between said iirst and second ramchambers, automatic pressure-sensitive valve means disposed in saidconnecting passage means in pressure communication with said second ramchamber, said valve means having an open condition maintained at above apredetermined pressure in said second ram chamber and a closed conditionmaintained at below said predetermined pressure, said valve means insaid open condition permitting flow of hydraulic fluid in the directionfrom said second ram chamber to said first ram chamber, and in saidclosed position preventing such W, a source of hydraulic fluid underrelatively high pressure in permanent communication with said second ramchamber, a control valve operable to control release of hydraulic -iluidand communicating with said References Cited in the le of this patentUNITED STATES PATENTS 2,381,923 Obstresal Aug. 14, 1945 2,645,960Hutchinson July 21, -1953 2,770,222 Anderson Nov. 13, 1956 FORElGNPATENTS 828,188 Germany Ian, 17, -2

